This is how one of my metrics is defined:
But, in the query builder, this is how it is shown:
If I do not define an alias, though, the definition will be shown properly, but, when I run the question, my column will be named "sum", which is hardly helpful in any case.
So, my suggestion: either show metric columns name as the metric name by default, even if an alias is not defined, or show the metric definition in the question tag thing, even if a metric is defined.
I googled it quickly and couldn't find any issue or post here. If no one points any similar request, I'll file an isuse on git.